Just make sure to remove the AAA batteries when not using the calc for a long while (especially years), else they slowly die then start leaking, which can cause permanent damage to circuits. In fact, I sometimes had leaking batteries after only half a year of non-use. It's worse in newer calcs it seems.

Logged

In case you are wondering where I went, I left Omni back in 2015 to form CodeWalrus due to various reasons explained back then, but I stopped calc dev in 2016 and am now mostly active on the CW Discord server at https://discord.gg/cuZcfcF

Hopefully this isn't too necrotic, but it's definitely relevant.I picked up a TI-81, S/N 1210793 and an unreadable-from-pictures date code. It has the blue-on-green screen, and takes a backup battery. Once it arrives I will do some analysis of it. I have noted that the very early models (such as the pre-1991 models without a backup battery) with no letter after the date code have the gray-on-white screen seen on the later models. Using the blue-on-green screens must have been a short phase in the TI-81 life cycle.

A bunch of pictures of various calculator screens, contained in 40 MB of wonderful PNG quality, can be found here. Included are these two TI-81s, two TI-82s (one with old display hardware, the other with new display hardware), a first-generation TI-83, first-generation TI-85, and my Nam Tai-produced TI-86.Also of note is that there are 40 contrast steps on the HW-'B' TI-81, but just 10 on the HW-'F' TI-81.